A new tool that uses a forest-like array of vertically-aligned carbon nanotubes that can be finely tuned to selectively trap viruses by their size can increase the detection threshold for viruses and speed the process of identifying newly-emerging viruses. The research was led by an interdisciplinary team of scientists at Penn State. "Detecting viruses early in an infection before symptoms appear, or from field samples, is difficult because the concentration of the viruses could be very low -- often below the threshold of current detection methods," said Mauricio Terrones, professor of physics, chemistry, and materials science and engineering at Penn State, and one of the corresponding authors of the research. "Early detection is important because a virus can begin to spread before we have the ability to detect it. The device we have developed allows us to selectively trap and concentrate viruses by their size -- smaller than human cells and bacteria, but larger than most proteins and other macromolecules -- in incredibly dilute samples. It further increases our ability to detect small amounts of a virus by more than a hundred times." The research team developed and tested a small, portable device that increases the sensitivity of virus detection by trapping and concentrating viruses in an array of carbon nanotubes. Dilute samples collected from patients or the environment are passed through a filter to remove large particles such as bacteria and human cells, then through the array of carbon nanotubes in the device. Viruses get trapped and build up to usable concentrations within the forest of nanotubes, while other smaller particles pass through and are eliminated. The concentrated virus captured in the device can then be put through a panel of tests to identify it, including molecular diagnosis by polymerase chain reaction (PCR), immunological methods, virus isolation, and genome sequencing.